Berlin 2018 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 19: Solid-liquid interfaces: Reactions and electrochemisty II (joint session O/CPP)

CPP 19.1: Vortrag

Montag, 12. März 2018, 16:45–17:00, MA 144

Pt modified Ru(0001) electrodes: structure-activity relationship for the CO and MeOH electrooxidation — •Albert K. Engstfeld, Jens Klein, and R. Jürgen Behm — Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm

Bimetallic PtRu catalysts are the most prominent catalyst material in polymer electrolyte membrane fuel cells for the electrooxidation of methanol (MeOH) since it enables the oxidation of the strong binding reaction intermediate CO from the surface at much lower overpotentials compared to a bare Pt catalyst. The underlying process is attributed to a so-called Langmuir Hinshelwood bifunctional mechanism, where the CO oxidation from Pt and Ru sites is promoted by the preferential adsorption of oxygen on neighboring Ru sites. In this work, we will show in comparison the electrocatalytic CO and MeOH oxidation on well defined Pt-modified Ru(0001) electrodes (surface alloys and Pt sub-/multilayer structures), prepared under UHV conditions and characterized on an atomic scale level with scanning tunneling microscopy (STM). For the surface alloys as well as submonolayer Pt-modified Ru(0001) we will show that the formation of bifunctional sites is indeed beneficial for the CO electrooxidation but is surprisingly inactive for the MeOH electrooxidation. On Pt multilayer structures, thus a surface without bifunctional sites, the MeOH electrooxidation is significantly more active compared to the mixed surfaces. Based on these results we will discuss the rate-limiting steps for the MeOH electrooxidation on these surfaces and discuss the influence of related electronic and geometric effects on both the CO and MeOH oxidation.